Recently, applications and services provided by portable electronic wireless devices or by devices interacting with a portable electronic device carried by a user have become popular. It would be desired for some applications and services to know the location of the portable electronic device relative to the user and the orientation of the user.
As a whole, users of portable electronic devices, such as smart phones, carry their devices in a variety of different locations relative to their bodies when they are walking or standing. For instance, they may carry a mobile phone in their hand, trouser pocket or handbag. In general there is also a tendency for users to pay little attention to the orientation of a carried portable electronic device, especially when not using and interacting with the device. This means that, for most portable electronic devices, without imposing requirements on where and how a user must carry the device, which might be inconvenient to the user, information concerning the orientation of the device relative to the user, as well as the location of the device on the user, is not available to the device itself and also, therefore, not available to any applications running on the device or systems which might communicate with the device.
It is known to determine the orientation of a portable electronic device relative to the Earth, as well as its longitude and latitude. However, creating a suitable and practical means by which a portable electronic device could either determine its location on the body of a user without having to be at a certain orientation to the user, or determine its orientation relative to a user's body without having to be at a certain location on the user would be useful and would allow for significant further development of portable electronics technologies, for instance in new applications.
It is known to use a combination of accelerometers and gyroscopes within a mobile phone to estimate the location of the phone on the body of a user, for a number of different on-body locations, when the user is walking. However, in order to provide accurate results, these methods take a significant amount of time to execute and require a lot of computational processing. Gyroscopes are also prone to drift, which can introduce a growing error in their readings over time.
It is further known to estimate the direction (bearing) in which a user's body is facing by analysing a history of portable electronic device longitude and latitude positions recorded as the user moves. However these techniques are dependent on the presence of infrastructure external to the device, such as the Global Positioning System (GPS), which limits their use to environments with suitable reception. Further to this, frequent positioning with systems such as GPS demands a significant amount of battery power.
The invention was made in this context.